Life Sciences

WHEN FORM OUTLASTS ITS MEDIUM:

A Definition of LifeIntegrating Platonism and Thermodynamics

In Seckbach, J. (Editor) Life as We Know it.Dordrecht: Kluwer Academic Publishers, 607-620.

(2005)
When form outlasts its medium: A definition of lifeintegrating Platonism and
thermodynamics. Invited paper. In
Seckbach, J. (Editor) Life as We Know it.Dordrecht: Kluwer Academic Publishers, 607-620.

My own attempt to meet this challenge has taken a long
path. I began with writing down all the characteristics of the known living
organisms that seemed to be fundamental, shifting viewpoints between biology,
physics, and philosophy. Naturally, the resulting list was long, way far from
the categorical “Life is …” statements that most theorists are after. But as
time went by and I revised the list time and again, something began crystallizing,
perhaps not unlike the way a mathematician’s many-sheets scribbles eventually
converge into a single elegant equation. Finally, a new “Life is…” has emerged,
proposed here on Section 10.

Because some novel insights have been gained during
the various stages of this search, I present in this article the entire way of
thinking that has lead to the proposed definition.

2. A “Wet Biology”
Prologue

When
seeking to abstract life, to refine a single unifying principle that underlies
its countless manifestations, perhaps there is no better starting point than an
encounter with a living thing in the flesh – moving, moist, unexpected, even
offensive – like the one that I had not long ago. I was crossing a garden late
at night when, out of the carpet of dry leaves, pinecones and pebbles that
covered the ground, a toad suddenly leaped high and scared me for a moment. It
was this sudden movement of the little creature, which had been lying
motionless like all the other lifeless things surrounding it, which made me
acutely aware of its uniqueness amongst these inanimate objects. Spontaneity,
the capability of being the agent rather than the subject of
motion and change, is the first characteristic of life that meets the eye.

Surely, however, the toad was equally alive before
leaping, while sitting still. It was also alive during the summer months when it
laid dormant underground. Moreover, life dwells, though in different ways, also
in the grass and moss, and even in the seeds within the dry pinecones scattered
over the garden’s soil. The dividing line between animate and inanimate is
therefore not always as clear as in the case of a running, screaming and biting
animal, but it is surely there. What, then, is that state that makes something
“alive”?

3. Dry
Abstractions:Form Outweighs Intensity

Clearly, it was the spontaneity
of the toad’s leap that has made it so distinctly alive. Newton’s law relates
the change in a body's state to the force acting on it: F=ma, or a=F/m, where a
is the acceleration, namely, the change in the object’s motion (or rest), F the force exerted on it amd m its mass. Acceleration, then, is
proportionate to the force divided by the body’s mass. Hence, for a pebble to
leap as high the toad did, it would have to be given an appropriate kick. The
toad, in contrast, leaped by itself, the only external “force” acting on it
being a few photons that impinged on its retina. The acceleration in this case
has no proportion to the physical magnitude of the external force which has
initiated it.

Of course, the conflict is only
superficial: The organism, using energy resources within it, exerts additional
force on itself in response to the minor force from outside. But here a genuine
hallmark of life emerges: It is the form of the external action, rather
than its magnitude, that determines the magnitude of the organism’s
reaction. The light falling on the toad’s eye from the garden’s lamppost, for
example, was much stronger, yet it did not elicit the frightened response as
the weaker light coming from the approaching human. So, if viewing the organism
as one whole – ignoring for a moment its being composed of numerous different parts
– we can point out a crucial difference between an inanimate and an animate
object. The former reacts to the sheer magnitude of forces, while the
latter reacts to their configuration.

Notice, moreover, that
the configuration is largely independent of its medium. In the case of the
toad, another form of energy (sound, scent, etc.) may elicit the same response
if it carries the same warning.

4. Generalizing:
The Living Form Outlasts its Medium

Much
as the above encounter confronts us with life's fleshy side, it also highlights
life’s abstract aspects. For more than two decades I have listened to toads
every autumn croaking from the garden's pond, occasionally even seeing a few.
Surely there were individual differences between their bodies and croaks, but I
failed to notice them. Numerous toads, which to human perception are
indistinguishable from the one I saw, inhabited that garden for many years,
begetting one another, till the one that I encountered. It is the form
which has prevailed, while individual animals came and perished.

This ability of form to outlast its substance appears
even ontogenetically, during the life of the individual organism. The toad
which I saw has probably exchanged all its molecules within the last few years,
but it has retained its form. To be sure, it has been an embryo and then a
tadpole, and later grew up till reaching its adult size, but even during those
intermediate stages the toad’s form outlasted (at least partially) the matter
of which it was made.

Note that “form”
equally refers to the toad’s croaks and leaps. It therefore denotes not only
spatial structures but temporal patterns as well.

These observations cannot fail to remind us of Plato’s
philosophy, where the concept of form, and that of ideas in general, featured so
prominently. For Plato, pure form had greater reality than the concrete objects
molded in that form. Similarly, ideas existed prior to their material
realization. Abstract forms and ideas, not material objects, are the foundation
of reality, which is why an abstract discipline such as mathematics is so powerful
for mastering the physical world.

Aristotle took exception with this view, reasonably
arguing that forms cannot exist without some matter of which they ought to be
made. Yet Aristotle was an avid biologist, and it is very likely that his lasting
preoccupation with taxonomy and with the notion of a species reflected his
attempts to struggle with his mentor’s challenge. This is even more evident in
his speculations about the formation of the embryo, where the interaction of
“form” and “matter” (roughly equated to “male” and “female,” respectively)
somewhat echoes Plato’s thinking.

We need not go deeply into this ancient debate when
seeking for a definition of life. Yet it is very striking that Plato’s argument
has a close affinity to two of life’s most prominent hallmarks, namely,
reproduction and metabolism. In both cases the same wonder occurs: Matter
assembles and disassembles with the inflow and outflow of matter into the
living body, and with the births and deaths of countless individual bodies, but
the form prevails.

5.The Thermodynamic Aspect: The Living Form Feeds on Information

Plato’s ideas referred
to a world which is, by definition, ideal. As our world is far from that, we
must complement Platonism with the branch of physics that studies just what
makes our world so far from ideal. Thermodynamics studies, inter alia,
the increase of entropy, which degrades all forms into chaos. Oddly, however,
it is the thermodynamic laws that enable life not only to preserve forms
against degradation but even to refine and improve them. Thermodynamics shows how,
alongside with matter end energy, the living organism processes a third vital
currency, namely, information (Elitzur, 1994, 1995; Lahav et al., 2001). A
brief introduction to information’s role in life would therefore be in order.

For a diver’s watch to
be waterproof, its designer must use a great deal of information about the
conditions undersea. What, then, about a fish? The question makes us realize
that “adaptation” means that a great deal of information has been incorporated
in the adapting species’ genome. Information processing, therefore, underlies
evolution, an insight that we owe to the famous “Maxwell’s demon” paradox (Leff
and Rex, 1990). Consider a closed box, full with gas in equilibrium and divided
by a partition into two halves. A tiny demon within the box directs the gas
molecules’ motions by opening and closing a microscopic door in the partition.
Eventually, hot gas forms on one half of the box and cold gas on the other.
Entropy has been reduced. But such a reduction normally requires a
proportionate energy investment that would increase entropy elsewhere, in
compliance with the Second Law. For the demon, however, the energy required for
sorting molecules is negligible. A violation of the Second Law seems to ensue.

The paradox was resolved
once it was pointed out that the demon needs information in order to
perform its task. The acquisition of this information (or, more precisely, the
repeated erasure of old bits for receiving new ones [Leff and Rex, 1990]) has
its cost in energy, which increases entropy more than the entropy reduced by
the demon’s sorting. From this principle, which assigns an energetic price to
information, a complementary principle follows: The use of information can save
energy. For example, when we open a lock with a key we utilize the information
embedded in the key, which makes the enormous force needed for breaking the
lock unnecessary (someone else, of course, has already paid the energy cost of
engraving the information on the key).

Biological adaptation,
I suggest, abounds with such uses of information for saving energy. A tiger,
for example, exerts enormous mechanical force to kill its prey. But in the same
jungle dwells a cobra that can kill the same prey by merely spitting into its
eye. What is striking in the latter case is the apparent disproportion between
the negligible force exerted by the predator and the fatal result suffered by
the prey. The secret lies in the snake’s choice of the appropriate neurotoxin
(in this case, cobrotoxin) that precisely matches the acetylcholine receptors
at the ends of the prey’s muscles. Similar precision is manifested by the
choice of the vulnerable point in the prey’s body (once the venom has
penetrated the prey’s eye, its own vascular system carries it from there over the
entire body!). In other words, the cobra makes spectacular use of information
about its prey’s physiology and neurochemistry, thereby saving the energy that
the tiger would have to invest for the same purpose of bringing the prey down.
Notice that the tiger is taken here merely as an arbitrary baseline for
assessing the cobra’s efficiency; the tiger’s is also a successful organism and
its onslaught is also aided by a great deal of information. Still, the force
exerted by snake’s venom, in comparison, is literally infinitesimal – of
molecular scale. It suffices because it is exerted, thanks to the utilization
of information, with enormous precision. Of course, the acquisition of this
information was paid dearly by the snake’s ancestors during the species’ evolution,
enabling their fortunate descendant to save energy nowadays.

We can therefore
formulate the utility of information thus: With the aid of information, it
is possible to perform a given work with much less energy than in the absence
of information, as this little energy is invested at the right place and/or at
the right time. Living organisms, then, are lawful Maxwell demons: They
save energy by using information, the energetic price of which being already paid
by earlier generations during the harsh struggle for survival.

6. Maxwell`s
Demon in Action: Life Operates at the Micro-Level for Macro-Effects

With the above principles
in mind, the toad’s sudden spontaneous leap, which appeared to be such a unique
characteristic of life, can be illuminated in a new light. If the living
organism is a lawful Maxwell demon, then, with the aid of the information, it can
act at the microscopic level, producing numerous microscopic effects which then
converge into one large macroscopic effect. It is on this small-scale level,
unknown to our ancestors, in which one of the most important features of life
lies. Medieval thinkers argued that an organism is alive because a non-material
soul dwells in it. Their rationale was that there is no material difference between a living
toad and one that had just died. It seems to be the same object in both states,
hence the only difference could be the soul that has perished or left the body.

The modern answer to
this challenge of dualism is based on what we have learned about life’s
microscopic level since then. What seems to be a homogenous tissue of a leaf, a
bone, etc., is in reality a myriad of enormously complex cells, resembling one
another in numerous molecular details, eventually succumbing to death but
promptly being replaced by new, almost identical ones. Death of the organism
occurs when minute changes, too small and too many to be reversed or
even noticed, occur together in numerous cells. It is this microscopic
process, occurring immediately after death, which, unknown to our ancestors, gave
them the impression that a non-material agent was moving life. Living forms, then,
are maintained due to the great precision orchestration of their myriad microscopic
mechanisms (Dolev and Elitzur, 1998).

The uniqueness of the
biological motion is now illuminated in a new light. Compare the toad’s leap
from the ground with the opposite occurrence of a pebble falling on the ground.
In the latter case, a highly ordered motion of the macroscopic object degrades
into a myriad of disordered motions (i.e., heat) of the ground atoms, in
compliance with the Second Law of Thermodynamics. In the toad's leap, however,
something extraordinary occurs: Numerous microscopic interactions between
actin and myosin molecules within the toad’s muscles converge into one
macroscopic movement!

Another hallmark of
life thus emerges. The macroscopic manifestations of life are always a mere tip
of a microscopic iceberg. This holds even for micro-organisms, as their collective
actions lead to macroscopic phenomena, such as a lake turning green due to
algae or a human succumbing to influenza. Life gives rise to an extremely
precise cooperation between numerous microscopic motions, separated in space
and/or time, orchestrated so as to converge into the same large-scale outcome.

7.Platonism Again: Forms
Transcend Space and Time

The living organism,
then, is not a “thing” in the ordinary sense. Whereas a rock is a rock and an
iceberg is an iceberg only as long as their matter does not disintegrate, a
toad remains a toad even though its matter keeps
disintegrating; it is its form that prevails. And whereas the rock’s or
iceberg’s interactions with other objects are determined mainly by their gross
physical characteristics, such as mass and velocity, the toad’s interactions
are more determined by the minute atomic details of its DNA, the poison
molecules in its paratoid glands, or
the neurotransmitter secretions in its synapses. The living form thus assumes a
causal role in itself, just like mass, momentum and charge. In fact, life
enables the organism’s form to largely override its more fundamental physical parameters.

This realization should
pervade our use of biological notions. “Self preservation,” for example, means
that the organism preserves its form and not its matter. Similarly “survival of
the fittest” favors not the fittest individuals but the fittest makeups. And a
“selfish gene” in the form of a particular DNA segment often leads to its own destruction
in favor of copies of it elsewhere. In short, metabolism and reproduction, life’s two most prominent features, are
two aspects of form’s supremacy over its medium.

Once a form is
considered to be a thing, just like a concrete chunk of matter, an important
distinction emerges between the two kinds of things. A material object can
reside only in one place at a time. Not so with a form: If there are many
objects with exactly the same form, then there is one form that exists in many
places at the same time!

This formulation might
sound like a mere play of words, but in the next section I will show that it is
this illocality of form that enables life to increasingly transcend space and
time limitations. Notice, first, that illocality is already implicit in our
biological parlance. When we say that “the gene BRCA1 is responsible for breast
cancer” or “thefoxiscommon in the
British Isles,” we do not refer a certain DNA segment within some individual
cell, nor to a particular animal, but to one form whose copies abound in
numerous places and times. True, the biological form is a far cry from Plato’s
ideal forms that reside out of space and time, and yet it is able to gradually
transcend space and time limitations.

The Platonic and the
thermodynamic aspects of life now begin to converge. Since the organism is not
an ordinary chunk of matter but a form that survives its matter, and since form
can reside in numerous places at the same time, this illocality of form enables
the information accumulated within the organism’s genome to become increasingly
more valuable.

But how can one
quantify the information value of a certain DNA sequence? This is a highly
disputed issue, which we can avoid by addressing one special aspect of
information, namely, the scope of its relevance. The Cobra’s venom is so
powerful because it matches the nervous systems of all vertebrates.
Consider next plants’ geotropism, namely, the mechanism that enables the
organism to sense the direction of the gravitational force. Many plants develop
individual forms in adaptation to the local conditions, e.g., the ground’s
slope or sunlight’s direction. Yet a few trees, such as the fir and the
cypress, have a uniform shape which is largely independent of the local
conditions. Interestingly, these uniform trees always grow straight upwards, as
they rely mainly on gravity, which is the same everywhere. In fact, the
evolution of geotropism means that “knowledge” of gravity was long ago obtained
by the plant’s genome, for, had Newton’s G been other than 6.67 x 10-11
N m2/kg2, the statoliths within the plant’s cell would
fail to properly sediment in the ambient fluid. Here again, the organism gains
information about a feature of the environment that prevails in all
locations, on Earth, in all times.

In some cases the
information accumulated in an organism’s genome is so subtle, hence so
abstract, that it can surprise even the human mathematician. Take, for example,
the 13-years
cicada and its relative, the 17-years cicada. The nymphs of these species develop below ground and
after 13 or 17 years they emerge and molt to the adult stage. Their massive
brood emergence is believed to overwhelm predators, which are mostly birds.

Is this just another example of sibling species? No, for there are three different cicada species,
each having a 13- and a 17-years subspecies (Grant, 2005; Williams and Simon, 1995). Clearly, these species could
not have simply evolved from one another, because each species could have evolved
from either the 13- or the 17-years subspecies of the other species, leaving
the emergence of the complementary 17- or 13-years subspecies unexplained. It
is evolution, then, that has come up, three times, with the same pair of
primary numbers in its search for numbers that do not divide into smaller
numbers, mainly in order to prevent convergence of prey’s and predator’s
life-cycles (Dawkins, 1987; Gould, 1977).

These examples
demonstrate an essential feature of biological information: This information
concerns invariant features of the environment (Elitzur, 1997). The
information encoded in the cobra’s venom does not concern only an individual
animal, nor a particular species, but something common to all
vertebrates. The information encoded in the plant’s geotropic mechanism is
valuable everywhere. The information used by the cicada concerns the
life cycles of all its predators. The latter case exhibits an even more
invariant kind of information: Numbers are the subtlest aspect of physical
reality! In fact, evolution gives a very profound clue as to how such a level
of abstraction has been reached: The cicada has obtained information not merely
about its environment but about the information obtained by other
information-processing systems – higher-order information, so to speak. First, the
cicada’s predators have “learned to count the years” so as to establish their
specific life cycles, in order for all males and females of the same species to
reach sexual maturity at the same time. Then, after these numbers were taken, the
cicadas had to “find” the numbers that do not divide with any of these cycles.
This sequence is not much different from the way human arithmetic developed
over the centuries: The ancient discovery of numbers has later enabled the recognition
of special numbers such as primary numbers, whose properties were derived from
those of the ordinary numbers. Plato would probably be pleased to learn that
numbers have played a role in the lives of insects long before the appearance
of human arithmetic!

Evolution, to
reiterate, is a process by which information about the environment is
accumulated in the species’ genomes, and this information’s relevance becomes increasingly
broader. We are now in a position to prove a more specific hypothesis: Evolution
is a very efficient mechanism for extracting environmental information out of
the environmental noise. A simple analogy would serve as a useful
introduction. Consider the light coming from a distant star. Its information
content is poor. The reason for this is not, as one might think, the light’s
weakness; light can easily be amplified. Rather, it is the fluctuations
(atmospheric and optic), that pollute the information carried by the star’s dim
light. In other words, the information coming from the star is inflicted with
random noise. For the small human pupil, this signal-to-noise ratio is too
great to resolve. The Newtonian telescope overcomes this difficulty with the
aid of a large concave mirror, up to a few meters, that collects the light signals
over a large area and concentrates them on the telescope’s lens. Here an
efficient resolution of signal from noise takes place: The constant signals
(coming from the star) are additive, while the random fluctuations (caused by other
factors) are much less so. Let s and Δs denote
signal and noise, respectively. Then, joining the radiation coming from n
points,

Noise thus “cancels
our” in comparison to the strengthening of the signal. The same principle is
utilized by all antennae.

The biological analogy
is clear. Consider a single, only slightly advantageous mutation. At the
individual level, this mutation can hardly affect survival; an organism
possessing it might happen to fall victim to an accidental calamity while an
organism lacking it might survive by sheer luck. If, however, the mutation has
managed to be replicated in large numbers within a certain population, the
above dynamics takes over. With n being large (many organisms over many
generations), even the slightest advantage will eventually gain dominance over
the population. In information theory terms, the weak environmental feature
that gives a slight advantage to the mutation is amplified by evolution. Elsewhere
(Elitzur, 1994) I have pointed out several other such “proto-cognitive”
capabilities of evolution.

Let us summarize: Alongside with
matter and energy, organisms constantly process information. It is common knowledge that the genome contains
information as to how the organism should be assembled. But as Maynard-Smith
(1999) has pointed out, this information is useful only by virtue
of its reference to the particular environment in which this organism
must live. The
central concept of evolutionary theory, namely, adaptation, thus gains a novel
meaning. Adapting to a certain environment necessitates, first and foremost,
reliable quantitative information about it.

9. Inventorying the Hallmarks
of a Living Organism

Based on the above
discussions, we are ready to prepare a tentative inventory of the physical
attributes of the living organism, leaving the definition of life itself for
the next stage. Which of life’s hallmarks should come first? Rather than trying
to assign them any order of importance, let us adopt a more pragmatic order:
First let those properties that immediately meet the eye be pointed out. Next shall
come the properties that appear over longer observation periods and those that
are revealed when going down to the smaller scale level. Still, as the
recurrent cross-references below indicate, life itself defies any attempt to
describe it in a linear order.

A Living Organism, then, is a system in which Life is embodied by
exhibiting the following properties:

3.COGNIZANCE: The organism’s
reaction to external force does not follow the straightforward F=ma
relation, as its own resources of potential energy release additional force
during the reaction. Its reaction, therefore, depends not only on the external
force’s magnitude but on its configuration as well.

5.SELF-ACTION: on the organism itself. In the long run, all
the organism’s actions eventually affect itself,

6.PERPETUATION: preserving its selfhood (ý1) through

7.METABOLISM: incessant replacement of parts of the organism that
leave it, such that even when the organism’s form changes, it maintains its
integrity (ý1.1), animation (ý1.2) and organization (1.3); as well as

10.PROGRESS: systematically selected such that the organism’s properties
become more and more prominent.

11.INFORMATION PROCESSING: Together with matter and energy, the
living organism incorporates, stores, exchanges and processes information. This
information is accumulated during phylogeny (evolution) and/or ontogeny
(learning) and takes part in all biological processes. It is information
exchanged between the organism’s inner constituents that enables the organism
to maintain itself (ý1); it is information about surrounding events that
enables the organism to discern (ý3) events that bear on its survival, to anticipate (ý5) them and to adequately respond (ý4) to them; it is the information constituting the
organism’s blueprint that enables it to replicate (ý9); and it is information about a particular
environment that underlies adaptation to that environment. Biological
information increases the efficiency of any work carried out by the organism,
by the principle “less and less energy, but more and more precisely at the
right place and/or the right time.” Biological information eventually attains
higher value as

11.1.REFLEXIVITY: the living organism processes information not only
about its environment but also about other information-processing systems like
itself, thereby gaining higher-order information; and as

11.2.ABSTRACTION: the processing of environmental information reveals
ever more subtle regularities in the environment, i.e., patterns that are ever
more invariant in space and time, like natural law itself.

10. The Definition

Can an inventory of
characteristics – assuming that they are indeed essential – converge into a
concise definition?The main insight
inspired by the encounter with the toad, and later reflected in the inventory,
is that life manifests a striking degree of supremacy of form over its medium.
Each organism’s form is embedded, of course, in matter, but it outlasts
the individual chunk of matter in which it is embodied. Both metabolism and
replication are manifestations of this principle.

Based on this aspect
of life, here is the first attempt at definition:

“Life is a
process by which a form outlasts the medium in which it is embedded.”

Immediate objections
are expected. The living form does not remain unchanged, as organisms grow and
species evolve. But then, growth and evolution make the organism even more
capable of outlasting its medium, and of overriding the physical constraints to
which an inanimate object of the same mass and chemical composition would be
subject. A better proposal would therefore be

“Life is a
process by which forms become increasingly independent of the medium in which
they are embedded.”

By referring to
“forms” in plural our definition encompasses also the organism’s change of
form. It is, Platonically speaking, not just “a form” but “form” in general –
the idea of form – that outlasts its medium, thanks to life. The adverb
“increasingly” means that evolution makes forms more and more liberated
from the physical constraints of their medium.

Still, the definition
is not exclusive enough. A tornado is a very unique form, made of air and
debris which are constantly replaced by new air and debris, such that only the
tornado’s form remains and its power even increases. Yet a tornado is certainly
not alive. But we now recall that the supremacy of form over the medium holds
not only for the organism’s body but also for what this body reacts to, namely,
environmental information (see sections 5-8). Information, by definition, is
characterized by its configuration rather than by the type of matter or
energy in which it is stored or carried. As we have observed, the organism
reacts to the information itself rather than to its medium. This
property is much more typical of living organisms, and together with the above
characterization gives a sharper definition:

“Life is a
process by which forms become increasingly independent of the medium in which
they are embedded, by interacting not only with their environment’s matter and
energy but also by interacting with the forms, as forms, which are
embedded in the environment.”

Information, then, is
a special kind of form, which abounds in the organism’s environment, and the
living organism discerns and utilizes these subtle forms in order to enable its
own form to outlast its medium.

Information, however,
rarely appears in Nature in its ideal form. This is why, alongside with Plato’s
lofty ideas, we summoned also the mundane science of thermodynamics which
obliges form and information to constantly erode. In section 8 we pointed out
the way an evolving population overcomes this informational erosion and extracts
environmental signals from the environmental noise: Reproduction utilizes the
statistical advantages of large numbers in order to increase the signal-to-noise
ratio. We can therefore give our Platonic definition a last,
information-theoretical twist:

“Life is a process
by which forms become increasingly liberated of the constraints of their
material medium, thereby appearing in a multitude of places and times, thereby
interacting not only with the local, random aspects of the environment, but,
increasingly, with the invariant spatio-temporal regularities underlying Nature,
namely, physical laws themselves.”

Would this definition
prove satisfactory next time one encounters a living organism and wonders what
makes it alive? The answer must be left to you, the reader. The next animal or
plant that you will see has a unique form, assembled of numerous sub-forms,
patterns, rhythms and regularities in space and time. These forms last despite
the fact that the matter and energy of which they are made are constantly lost,
only to be replaced by other matter and energy, over and over again, yet the
form outlasts them all. And this form, which constantly interacts with other
things, interacts not only with the matter and energy of which these other
things are made, but mainly with their forms. Form gradually became liberated
from the physical constraints of its medium, though never fully independent of
it as in Plato’s world of ideas. So when human thoughts long survive their
originators, in language, in letters and on the Internet, this is the most
natural consequence of what life is all about.

11. Requiem to the Toad: Life’s
Essence and Value

The living thing which
I encountered was a rather unassuming species, grey-brownish, moist and coarse.
But some other members of the order Anura, to which toads and frogs
belong, are among the most beautiful creatures on Earth. Their striking colors
signal that they are highly poisonous, which means that highly valuable medical
information about us, their most menacing enemies, is concealed in their skins.
Unfortunately, most of this knowledge is being rapidly lost to humanity. Anura
and all amphibians are going extinct all over the world (Houlahan et al., 2000).
The devastation caused by humans to the biosphere are changes to which these
little creatures turn out to be most vulnerable. Ecologists keep warning us
that these species are only early indicators of a global catastrophe that
threatens all life on Earth, us as well.

Much as the definition
of life’s essence is elusive, the search for its essential physical
characteristics seems to enforce on our mind also life’s value. Life is
unique, amazing, precious – and sacred.

12.Acknowledgements

It is
a pleasure to thank five anonymous referees plus one chief editor for many
valuable comments. Thanks are due to Harald Atmanspacher and the Institut für
Grenzgebiete der Psychologie und Psychohygiene at Freiburg, where the last
version of this article has been completed. I dedicate this work to the memory
of Shneior Lifson (1914-2001), my
sorely missed mentor and friend.